Document Type


Date of Degree Completion

Fall 2022

Degree Name

Master of Science (MS)


Geological Sciences

Committee Chair

Walter Szeliga

Second Committee Member

Breanyn MacInnes

Third Committee Member

Timothy Melbourne


The seismicity in the Basin and Range Province of the western United States often manifests as clusters of earthquakes occurring over brief windows of time, lasting from months to years. Two different earthquake clusters occurring between 2014 and 2018, near Challis, Idaho and northwestern Nevada, were assessed in this study. The seismic activity in the southeastern section of the Challis cluster began with a M5.2 earthquake that was likely the main-shock earthquake in an aftershock sequence. The northwestern section of the Challis cluster does have several potential candidates for a main-shock earthquake, but none have been identified as a start to a true aftershock sequence, and there is no distinct spatial progression noted. Similarly, the Sheldon cluster also does not have a distinct spatial progression or main-shock earthquake. Using the classification method described by Vidale and Shearer in their 2006 paper, I analyzed the statistical, temporal, and spatial characteristics of both clusters to see how these two clusters compare. For the Challis region, the two sections of the cluster appear to have different driving mechanisms. While the northwest cluster falls under the “average” classification, the southeast cluster is categorized as “aftershock-like” sequence, suggesting that the southeast cluster is related to the Lost River Fault System. The northwest cluster’s seismicity may be due to hydrothermal activity, as there are several hot springs in the area. The Sheldon cluster, whose hypocentral distribution resembles a tube or a ball when mapped in 3D, falls under the classification of “swarm-like.” The driving mechanism for this cluster is more difficult to determine, as there is no history of seismicity in this area, though there is some history of relatively recent magmatism and some currently active hot springs.